Question No$.2$

A three$-$phase. $60-Hz$ induction motor runs at $890\frac{r}{m}in$ at no load and at $840\frac{r}{m}in$ at full load.

$($a$)$ How many poles does this motor have?

$($b$)$ What is the slip at rated load?

$($c$)$ What is the speed at one$-$quarter of the rated load?

$($d$)$ What is the rotor's electrical frequency at one$-$quarter of the rated load?